Each surface of the human body, which stays in contact with the external environment, is covered by a layer of microorganisms. This layer-the human microbiomeis characterized by a high diversity of species and huge number of cells. Its name was proposed by Joshua Lederberg at the turn of the twentieth and twenty-first centuries and was originally referred to as a group of microorganisms colonizing a certain habitat. Currently, the term also defines a set of genomes of all organisms inhabiting a particular niche. Since the human microbiota affects many aspects of human health, it has become the subject of different studies. The use of sequencing methods enabled to obtain genetic material derived directly from the human environment with simultaneous explanation of mutual relationships between microorganisms inhabiting different ecological niches of human organism (i.e., commensal, symbiotic, and pathogenic microorganisms). It is hard to determine the amount of microbiota inhabiting human oral cavity because microbiota represents distinct anatomically limited ecological niches; for example, microbiota of tongue surface, cheek, teeth, palate, gingiva, and periodontal pocket. Apart from anatomical structure, other factors determine different composition of particular oral cavity microbiota. These factors are various qualities of saliva-a natural protective barrier ensuring maintenance of healthy condition of the oral cavity-and habits of diet and hygiene. Generally, bacteria are passively transported by flowing saliva toward teeth surfaces. In turn, the pioneering microorganisms initiating changes in the environment of oral cavity through the production and secretion of products of their metabolism induce mutual microbiota-biofilm interactions. The formation of biofilm of the plaque is a complex and rapidly evolving process in which several stages of development can be distinguished arbitrarily: (i) reversible binding of bacteria to solid surfaces, (ii) production of exopolysaccharide matrix, (iii) irreversible binding to the surface, (iv) maturation of biofilm structure, (v) disintegration and dispersion of an organized structure, and (vi) the formation of new habitats. An oral microbiome